As for a control device for driving a motor such as a switched reluctance motor, there is known a motor control apparatus that counts pulse signals outputted by an encoder in synchronization with rotation of a rotor, detects a rotational position of the rotor on the basis of the count values, and sequentially switches an energized phase, to rotationally drive the rotor.
This kind of motor can only detect an amount of rotation (angle of rotation) from an activated position of the rotor on the basis of count values of output signals of the encoder after activation. Thus, the motor needs to learn an absolute initial position of the rotor in some way at the start of activation and decide the correspondence between the rotational position of the rotor and the energized phase.
For example, in a method for aligning an angle sensor of a switched reluctance motor disclosed in Patent Literature 1, two phases are simultaneously energized at the start of activation, and the rotational position of the rotor after the lapse of a predetermined time is set as a reference, to decide the energized phase.